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5) Post-Harvest > Lecture 16: Composition of fruits and veg > Flashcards

Lecture 16: Composition of fruits and veg Flashcards

1
Q

max moisture content at complete turgor yield ____ turgidity

A

max

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2
Q

how can a plant have complete turgor?

A

having unlimited supply from mother plant

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3
Q

describe the conditions (TSS, OP and TP) at a very tender stage of a crop

A

low total soluble solids (TSS)

low OP

low TP

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4
Q

describe the conditions for optimal maturity stage of produce

A

high OP and TP = high turgidity

- balanced starch, celulose and pectin

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5
Q

describe the conditions of overmaturity/ripening

A

fruits:
- breakdown of starch and pectin
- loss in cell wall strength
- decr in turgidity

veg

  • sugar becomes starch
  • loss of TSS
  • low OP
  • low turgidity despite high cell wall strength
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6
Q

what is imp about dietary fiber consumption?

A
  1. provides non-digestable bulk to the diet
  2. helps to control appetite = incr retention time for nutrients
  3. restricts calorie food intake
  4. delays absorption of glucose and fat after a meal
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7
Q

what are 2 main categories of dietary fibers? example of each?

A

insoluble: cellulose, hemicellulose, lignin
soluble: pectin and gums

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8
Q

describe resistant starches

A
  • new class of fiber
  • not easily digestible
  • retains longer in the system
  • good for diabetic patients
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9
Q

describe straight chain starches

A

amylose w/ alpha 1,4 bonds

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10
Q

describe branched chain starches

A

amylopectin (alpha 1-4 and 1-6 bonds)

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11
Q

what bonds does cellulose have

A

beta 1-4 linkages

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12
Q

what major enzymes breaks down starches?

A

amylase and beta-galactosidase

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13
Q

industrially, starch is obtained from what?

A

potato and corn

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14
Q

describe pectic substances

A
  • imp for texture of produce due to structure forming ability
  • polymer of methyl ester of galacturonic acid
  • forms gel or viscous colloidal suspensions (eg. jam = pectin + sugar + acid + cooking)
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15
Q

what are rich sources of pectin?

A

apple and citrus fruits

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16
Q

what are 4 types of resistant starches?

A

RS1:

  • physically inaccessible or digestible
  • found in seeds and unprocessed whole grains

RS2
- occurs in natural granular form (uncooked potato, high amylose corn, green banana)

RS3
- formed when starch containing foods are cooked and cooled (eg. bread or retrograded high amylose corn)

RS4

  • starches that have been chemically modified to resist digestion
  • not found in nature
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17
Q

what are main components of jam?

A

pectin
sugar
acid

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18
Q

what is LMP? describe it.

A

low methoxyl pectin

  • forms gel with Ca without sugars
  • used in making diabetic jellies
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19
Q

how does pectic substances affect fruit juices?

A
  • increases viscosity
  • incr cloudiness
  • colloidal suspension
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20
Q

what is PME? describe it.

A

pectin methyl esterase

- a natural enzyme that can hydrolyze pectin

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21
Q

how can you decrease cloudiness of apple juice?

A

increase PME to hydrolyze pectin

then inactivate it during pasteurization

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22
Q

what is calcium chloride treatment used for? how does this occur?

A

firming fruit slices

Ca forms a gel with pectin (LMP) to increase gel strength or structural rigidity

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23
Q

how does pectin affect filtration in juice making?

how can this be prevented?

A
  • it delays filtration

- can facilitate filtration by using PME to breakdown pectin and using amylase to breakdown starch

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24
Q

____ are the major components of the cytoplasm

A

protein

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25
Q

define dry weight basis

A

%DB = (wt x 100) / dry mass

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26
Q

define wet wt basis

A

%DB = (wt x 100) / wet mass

27
Q

during storage, how do proteins affect OP of AA? how does this affect nutrition of the crops?

A

lowers OP of AA

increases nutrition of crops

28
Q

what are common plant proteins?

A

albumins
globulins
gliadins
glutenin

29
Q

what does gluten consist of?

A

gliadins and glutenins

30
Q

what is gluten imp for?

A

dough rheology

31
Q

what are fats and oils prominent in?

A

protective tissues (cuticle, epidermis, corky layers)

32
Q

what does the nutritional value of a fat/oil depend on?

A

degree of unsaturation

33
Q

what are examples of oils rich in sat FAs?

A

coconut and palm kernel oils

34
Q

what are examples of oils rich in unsat FAs?

A

corn
peanut
olive
soybean

35
Q

how many double bonds are in oleic acid?

in linoleic?

in linolenic?

in stearic?

A

oleic: 1 DB
linoleic: 2 DB
linolenic: 3 DB
stearic: no DB (saturated)

36
Q

how are organic acids formed in F&V?

A

by products of metabolic activities

37
Q

where are organic acids normally stored?

A

in the vacuole

38
Q

what are dominant organic acids?

A

citric and malic

others: tartaric, oxalic, isocitric

39
Q

what is used as a common food acidulant? why?

A

lime and lemons

they have more than 3% organic acid

40
Q

what is EPA? describe it

A
  • eicosa pentenoic acid
  • omega 3 FA
  • found in large amounts in brain nerve
  • v imp in immune system function
  • found in oily fish, seeds and nuts
41
Q

how is vit A present in F&V?

how is it converted to vit A?

A

as pro-vitamin A (beta-carotene) which is converted to vit A in digestive system

42
Q

why is Ca in spinach not bioavailable?

A

it is bound to oxalic acid

43
Q

what are 3 major classes of pigments in F&V?

A

chlorophylls
carotenoids
falvonoids

44
Q

describe chlorophylls

A
  • normal green pigments
  • imp for photosynthetic activity
  • found in chloroplast (chlorophyll a and b)
  • broken down by enzyme chlorophyllase
45
Q

what color are carotenoids?

A

yellow, orange

they are masked by chlorophylls in green leaves

46
Q

describe solubility of carotenoids

A

fat soluble

47
Q

where is beta-carotene found?

lycopene?

xanthophylls?

A

beta-carotene: carrot

lycopene: tomato
xanthophylls: radish

48
Q

where are carotenoids most present in plants?

A

chromoplasts

49
Q

how does chlorophyll (green) become phyophitin (olive green)

A

loses Mg

gains H+

50
Q

how does phyophitin (olive green) become phyophobide (brown)

A

loses phytol

51
Q

how does chlorophyllin (bright green) become phyophobide (brown)

A

loses Mg

52
Q

how does chlorophyll (green) become chlorophyllin (bright green)

A

loses phytol

53
Q

how does chlorophyllin (bright green) become chlorins (purpurins colorless)

A

H+ or O2

54
Q

how does phyophitin (olive green become chlorins (colorless)

A

O2

55
Q

which pigment is responsible for bright colors in F&V?

A

flavonoids

56
Q

what are classes of flavonoids?

A

anthocyanins:
- red, blue, purple
- found in sap of fruits, stems leaves roots

anthoxanthins:
- yellow
- shade is pH dependent

catechins

leucoanthocyanins:: colorless but forms brown pigments

57
Q

what does the shade of anthocyanin depend on?

what colors are they in low, medium and alkaline pH?

A

pH

low pH: red
with increasing pH: violet
alkaline pH: blue

58
Q

where are anthocyanins found?

A

sap of fruits, stems, leaves, roots

59
Q

what happens when tannins reacts with skin?

A
  • produce tan color

- produced by polymers of catechin in reaction with proteins of skin

60
Q

what happens when tannins reacts w/ metal ions?

what is this commonly used for?

A

dark colors

used in making inks

61
Q

what is the dark color of coffee and tea from?

A

tannins

62
Q

what are anti-nutritional factors? examples?

A
  • foods that can cause allergies, loss in memory, convulsions, paralysis, etc…
  • eg. excessive consumption of cabbage can cause hyperthyroidism (decreases iodine absorption)
63
Q

how can you cope with anti-nutrients?

A

inactivate toxins by cooking

64
Q

what happens when soybeans are soaked before cooking?

A

it removes thermo-labile toxic peptides (protease inhibitors)

5) Post-Harvest (17 decks)

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